Working on the Smash Bros. series must be an absolute nightmare. The amount of approvals and checks that have to take place for some content has to be mind-boggling. I'm not sure how Sakurai manages to stay on top of it all! In an interview with EDGE, Sakurai opens up about the process of bringing third party characters into the mix, explaining the steps necessary to make those additions happen.

“There are cases where I will meet with the original creators myself once or twice, but in general communication is carried out through Nintendo. In addition, it wouldn’t necessarily be the original creator I would meet – rather like how I was directly involved with the Kirby series, but don’t know about other projects now. We’ve made various changes so that both cartoonish and realistic characters can appear on the same screen together with it seeming natural, and the characters still looking cool. Character movements are also developed with a Smash Bros. style first. The end result from this is then passed on for review by the other companies, so they can point out any problems for us to fix. Though there might be differences in what is regarded as acceptable in terms of Smash Bros. and in terms of the original series, in the end we try to find something that both sides will be happy with. What I’ve always thought throughout my time working on this series is that if what I make is of good quality, more people will support it. I can feel the expectations coming from both inside and outside the company that Smash Bros. Ultimate will be able to do it right.”

1. Does he like the character/franchise or is he friends with other company employees? No previous experience on Nintendo hardware necessary.
2. Hand over a suitcase of money to said company for use of their license.
3. Company sits back, laughing, for doing no work, having little or no history of being on Nintendo platforms, nor making any promise for future games.

4. Players get to enjoy a fun, iconic character in a series that's all about bringing the industry's all-stars together. Some players make up some arbitrary conditions about what qualifies a character as being worthy of inclusion and complain on the internet, but the vast majority are very pleased.

I hate to play devil's advocate... but that said, I'm going to. Didn't Sakurai reveal in the past that Snake's inclusion in Brawl came to be because his son loved the character while playing The Twin Snakes?

1999-2001
1. Kojima's son was a big fan of Smash Bros.
2. One day the kid supposedly asked his father "Why there are no characters you created in this game?" or perhaps "Which one of this you made Dad?, I wan to show off at school"
3. Kojima goes with with his good friend Sakurai and asks for Snake inclusion in the next smash game sometime after Melee was already finished.

2003
4. Probably by coincidence, a fairly high profile exclusive MGS remake that you can't play anywhere else was announced for Gamecubel.